Output Bias Adjustment; Dc Accuracy Adjustment; Frequency Response - Fluke 5220A Instruction Manual

5 220A
Instruction Manual

4-33. Output Bias Adjustment

This procedure is used to adjust the bias current for both the A6 Driver and the A7
Output. The bias adjustment (R13) is located on the A6 Driver PCB Assembly.
1. Connect the ac voltage calibrator to the front-panel VOLTAGE INPUT terminals on
2. Connect the load resistor (.1 ohm) to the enabled output terminals on the 5220A.
3. Connect the distortion analyzer input to the sense terminals on the load resistor.
4. Set the ac voltage calibrator for a 20 V rms, 1 kHz output.
5. Set the 5220A to the operate mode.
6. Measure the distortion and adjust R13 for a minimum indication. At the final setting,
7. Set the 5220A to the standby mode.
8. Disconnect the distortion analyzer and the load resistor from the 5220A.

4-34. DC Accuracy Adjustment

This procedure is used to adjust R3 on the A5 Preamplifier PCB Assembly. This
adjustment controls the accuracy of the dc output current.
1. Connect the precision shunt (.01 ohm) to the enabled output terminals on the 5220A.
2. Connect the DVM to the sense terminals on the precision shunt. Observe polarity.
3. Connect the output of the dc voltage calibrator to the VOLTAGE INPUT terminals
4. Set the dc voltage calibrator for an output of +10.0000 V dc.
5. Set the 5220A to the operate mode.
6. Adjust R3 on the A5 Preamplifier for a voltage reading in millivolts that is 10 times
7. Set the 5220A to the standby mode.
8. Disconnect both the dc voltage calibrator and the precision shunt from the 5220A.

4-35. Frequency Response

The following procedure is used to adjust the frequency response of the 5220A. The
adjustment is made at C4 on the A5 Preamplifier PCB Assembly.
1. Connect the precision shunt to the enabled output terminals on the 5220A.
2. Connect the true rms voltmeter to the sense terminals on the precision shunt.
3. Set the output of the ac voltage calibrator to 10 V rms, 1 kHz.
4. Set the 5220A to the operate mode.
5. Note the reading on the rms voltmeter.
6. Change the frequency of the calibrator output to 5 kHz.
7. Adjust trimmer capacitor C4 on the A5 Preamplifier PCB to obtain the same reading
4-14
the 5220A.
distortion should measure less than 0.04 %.
on the 5220A; positive to red, negative to black.
the calibrated value of the precision shunt in milliohms. The adjustment should be
within +0.002 mV dc of the calculated value. For example: if the calibrated value of
the shunt is 0.0100253, adjust R3 for a DVM reading of .100253 V dc or 100.253
+0.002 mV dc.
on the rms voltmeter as that noted in step 5.